<?php
$id = $_GET['id'];

?>

<form enctype="multipart/form-data" id="upload_form" action="target.php"
method="POST">
<input type="hidden" name="APC_UPLOAD_PROGRESS" id="progress_key"
value="<?php echo $id?>"/>
<input type="file" id="test_file" name="test_file"/><br/>
<input onclick="window.parent.startProgress(); return true;"
 type="submit" value="Upload!"/>
</form>